In March 2010, the Jets needed a cornerback to start alongside Darrelle Revis. They had just released their other corner, Lito Sheppard. So they traded a third-round draft pick to San Diego for Antonio Cromartie, who had been a first-team All Pro during his second season in the NFL, 2007, when he had 10 interceptions.

Cromartie’s four seasons with the Jets never saw him reach those heights, though he did make the Pro Bowl in 2012 and 2013, for the second and third times in his career, albeit as a questionable alternate last season.

He also helped the Jets make their second straight AFC Championship Game in 2010, and when Revis suffered a season-ending knee injury in 2012, Cromartie performed well as the Jets’ No. 1 corner — a role he continued to hold in 2013 after Revis was traded to Tampa Bay.

But Sunday, almost exactly four years since the Jets traded for Cromartie, they released him — an expected cost-saving move that probably marked an unceremonious farewell for one of the Jets’ most popular players of coach Rex Ryan’s five-year tenure.

History will look favorably on most of Cromartie’s accomplishments with the Jets. He totaled 13 interceptions, but never had more than four in any season. He struggled in 2013, partly because he strained his right hip flexor during the preseason and it nagged him for much of the year. Pro Football Focus rated him 103rd out of 110 NFL corners, and 109th in pass coverage.

Cromartie, who will be 30 years old next month, was due to receive a $5 million roster bonus this week. He was going to count $14.98 million against the Jets’ salary cap in 2014 — the final year of his four-year contract. That is an absurdly high cap figure for a corner of his age, coming off a lackluster year. Now, he will count $5.48 million in "dead" money against the Jets’ cap this season — a savings of $9.5 million.

The Jets currently have about $31 million in salary cap space for 2014, according to overthecap.com. That number will grow if they release quarterback Mark Sanchez and/or wide receiver Santonio Holmes. Both probably will be cut. Sanchez’s departure would save $8.3 million in cap room, while Holmes’ departure would save $8.25.

Cromartie wanted to retire with the Jets but expected to be cut because of his high cap figure. He could technically return for a significantly more modest contract, as outside linebacker Calvin Pace did last offseason after being cut. But there seemed to be a feeling of finality in the words he wrote on his Twitter account: "It’s time for a new chapter in my life. Saying farewell to a great organization and fan base."

If Cromartie is indeed gone for good, the Jets are now in the market for a veteran No. 1 corner, since Dee Milliner does not seem ready to assume that role. He floundered last season as a rookie, though he showed improvement in December with three picks in the final two games. The Jets’ No. 3 corner last season was Kyle Wilson, a first-round pick in 2010, but he has rarely appeared capable to start regularly.

The free agency negotiating window opened Saturday, and teams can begin signing free agents at 4 p.m. tomorrow. The best free agent corners are considered to be Tennessee’s Alterraun Verner, New England’s Aqib Talib, Indianapolis’ Vontae Davis and Denver’s Dominique Rodgers-Cromartie, a cousin of Antonio Cromartie.

Though the Jets’ defense mostly excelled last season, finishing 11th in the NFL in yards allowed, pass defense was its weak point. The Jets ranked 22nd in the league in passing yards surrendered, as opposing quarterbacks successfully picked on Cromartie with deep balls almost as often as they went after Milliner.

Gone were the days of 2010 and 2011, when Cromartie and Revis formed a formidable twosome and combined for 11 interceptions during those two seasons. With Ryan again essentially coaching for his job in 2014, despite receiving a contract extension, he probably will have to start over at a critical position that requires the type of elite athlete Cromartie once was — and hopes he can be again.

Ryan, in a statement released by the Jets, called Cromartie "one of the finest athletes I’ve ever coached," and said, "I wish him and his family the best."